1. Technical Field
The present invention relates to a substrate and a method for manufacturing the same, and a probe card including the substrate, and more particularly to a substrate and a method for manufacturing the same, and a probe card including the substrate, capable of increasing the recognition rate of alignment keys formed on a substrate to improve accuracy in a micro electro mechanical system (MEMS) process of forming a micro probe on the substrate.
2. Description of the Related Art
In general, a semiconductor device is manufactured by a fabrication process of forming, on a wafer, circuit patterns and connection pads for testing and an assembly process of assembling the wafer on which the circuit patterns and the connection pads are formed into respective semiconductor chips.
A test process of testing electric properties of the wafer by applying an electric signal to the connection pads formed on the wafer is performed between the fabrication process and the assembly process.
The test process is performed in order to remove a part of the wafer at which defects occur at the time of the assembly process.
A so-called tester applying an electric signal to the wafer and a so-called probe card functioning as an interface between the wafer and the tester are mainly used in the test process.
Between them, the probe card includes a printed circuit board receiving the electric signal applied from the tester, and a plurality of probes contacted with connection pads formed on the wafer.
In recent, a circuit pattern formed on the wafer by the fabrication process is highly integrated due to the increased demand for highly integrated semiconductor chips, and as a result, a distance between adjacent connection pads, that is, a pitch becomes very narrow.
In order to test fine-pitch connection pads, the probes of the probe card are also finely formed.
Hereinafter, a general probe card will be described in detail with reference to the accompanying drawings, FIGS. 1 to 7B, as follows.
As shown in FIG. 1, a general probe card 10 includes: a printed circuit board 1 to which an electric signal is applied from the outside; a space transformer (STF) 3 having a plurality of micro probes 2 contacted with connection pads of a test object (not shown) such as a semiconductor chip; and an interface member 4 electrically connecting the printed circuit board 1 and the space transformer 3.
Here, the space transformer 3 is an electronic circuit board electrically connecting the printed circuit board 1 and the plurality of micro probes 2 having a size of several tens of micrometers in the middle portion thereof. Several tens of thousands of highly integrated micro probes may be formed by using a micro electro mechanical system (MEMS) process and a semiconductor process.
In other words, referring to FIG. 2, the space transformer 3 made of a ceramic substrate is prepared, and a conductive material 31 is provided on an upper surface of the space transformer 3. Then, a photosensitive film (dry film resist (DFR)) 32 is attached onto the conductive material 31.
Then, the photosensitive film 32 is patterned by performing an exposure process using a mask 33 and a development process on the photosensitive film 32.
Then, an etching process is performed thereon, to remove a part of the conductive material 31 on which the photosensitive film is not patterned, and then, the patterned photosensitive film 32 is stripped off, thereby forming a land pattern on the space transformer 3. A plurality of micro probes are embodied on the land pattern, and thus a plurality of micro probes 2 can be formed on the space transformer 3.
Here, in order to perform an electric test process by forming several tens of thousands of highly integrated micro probes 2 on the space transformer 3 and contacting the micro probes 2 with fine-pitch connection pads of a semiconductor chip, the micro probes 2 need to be formed at accurate positions of the space transformer 3.
To achieve this, as shown in FIG. 3, an alignment key 3a may be formed on the space transformer 3. The alignment key 3a is recognized in the MEMS process for forming the micro probes, so that positions at which the micro probes are to be formed on the space transformer 3 can be accurately caught.
More specifically, referring to FIG. 4, a process of manufacturing the alignment key and the micro probes on the space transformer will be described as follows.
First, a space transformer (STF) is prepared, and then a laser process is performed on the space transformer to form an alignment key at an outer perimeter region of the space transformer.
In addition, in order to perform an MEMS process well or the like on the space transformer, a surface of the space transformer is polished and then the alignment key is recognized, so that positions at which the micro probes are to be formed on the space transformer 3 can be accurately caught.
Then, the above-described MEMS process is performed to form micro probes at the micro probe formation positions caught on the space transformer.
Here, a surface of the spacer transformer is polished by about 30 to 40 μm, in order to remove foreign particles on the surface of the space transformer and smoothly perform the MEMS process. At this time, as shown in FIG. 5, the alignment key 3a is polished together with the spacer transformer 3, with the result that, after the polishing process of the space transformer 3, the alignment key 3 is removed or a shape thereof is changed.
In other words, the alignment key 3a is clearly recognizable before the polishing process of the space transformer 3, as shown in FIG. 5A, but the alignment key 3a may be damaged and unrecognizable after the polishing process of the space transformer 3, as shown in FIG. 5B. As such, since the alignment key 3a is difficult to recognize when the MEMS process is performed on the space transformer 3, it is difficult to catch the positions at which the micro probes are to be formed on the space transformer 3.
For solving this, as shown in FIG. 6, the alignment key 3a is formed more deeply at the time of processing of the alignment key 3a in the space transformer 3, considering the polishing process depth.
In other words, in a case where the polishing process depth of the space transformer 3 is about 30 μm, the alignment key 3a is processed to have a depth of about 50 μm.
However, in the case where the alignment key 3a is deeply processed, the working force of laser becomes strengthened and the number of processes becomes increased, and thus, the alignment key 3a becomes partially melted and collapses due to the heat of the laser, as shown in FIG. 7A. As a result, the recognition rate for the alignment key is decreased, and thus, it is difficult to precisely and accurately form the micro probes on the space transformer 3.
Furthermore, when the polishing process is performed on the space transformer 3 while the alignment key 3a is partially melted and collapses, foreign particles, that is, ceramic pieces or the like, which are generated when the space transformer 3 is polished, are put in a groove of the alignment key 3a, as shown in FIG. 7B. As a result, the recognition rate for the alignment key is decreased, and thus, it is difficult to precisely and accurately form the micro probes on the space transformer 3.